In a study of 32 people with heart failure, the 14 patients who felt the most depressed had nearly twice the levels of this protein in their blood.

The protein, tumour necrosis factor alpha (TNF-alpha), is one member of a large family of cytokines. The cytokines often cause inflammation in their effort to repair an injured or infected area of the body. In the case of heart failure, this inflammation makes it even more difficult for the heart to pump blood.

“People with heart failure typically have much higher TNF-alpha levels than people without the disease,” said Amy Ferketich, the study’s lead author and an assistant professor of public health at Ohio State. “But depression seems to make levels of this cytokine even higher, which is bad for patients.”

They recruited 32 patients from the heart failure clinic at Ohio State. The participants answered the 21-question Beck Depression Inventory, a tool that physicians and scientists use to measure symptoms of depression. The researchers drew blood samples from each patient. From these samples they evaluated levels of three cytokines: TNF-alpha, interleukin-6 (IL-6) and interleukin-1beta (IL-1beta).

Indeed, all of the patients in the study had higher-than-normal levels of each cytokine. However, TNF-alpha was still markedly higher in patients who reported feeling depressed on a regular basis.

“We were surprised to find that this wasn’t the case for the other two cytokines,” Ferketich said. “That suggests that something about depression may trigger the production of TNF-alpha.”

“Depression clearly raises the levels of one cytokine, which plays a role in increasing inflammation,” Ferketich said. “What we don’t know for sure is if depression causes the inflammation which may lead to heart failure or if heart failure causes depression which accelerates inflammation.”